1. Field of the Invention
The present invention relates to an abrasive member, and more particularly to an abrasive member for use in abrading the surface of an electrophotographic image-holding member.
2. Description of the Prior Art
An electrostatic image or toner image is formed by various electrophotographic processes. As the image-holding member on which an electrostatic image or toner image is formed, there may be mentioned an electrophotographic photosensitive member and other image-holding members.
The electrophotographic photosensitive members of various constitutions are prepared according to the predetermined characteristics of the members and electrophotographic process to be applied thereto. As typical photosensitive members, there are a member having a photoconductive layer formed on a support and a member provided with an insulating layer on the surface of the former member. These members are used in wide fields. The photosensitive member consisting of a support and photoconductive layer is employed in the image formation based on the most general electrophotographic process which comprises the charging, image exposing and developing steps, and further transferring step if desired. As for the photosensitive member provided with an insulating layer, such layer is formed for the purpose of protecting the photoconductive layer, improving the mechanical strength of the photosensitive member, bettering the dark decay characteristic of the member, or adapting the member to the specified electrophotographic process. Typical photosensitive members having such an insulating layer or examples of the electrophotographic process using the member having an insulating layer are disclosed, for example in U.S. Pat. No. 2,860,048 specification, Japanese Patent Publication Nos. 16429/1966, 15446/1963, 3713/1971, 23910/1967, 24748/1968, 19747/1967 and 4121/1961.
To the electrophotographic photosensitive member, the predetermined electrophotographic process is applied so that an electrostatic image is formed, and then it is visualized by development.
Some of the typical image-holding members other than the electrophotographic photosensitive member will be given below:
(1) Image-holding member used in the electrophotographic process which comprises forming an electrostatic image on a photosensitive member, transferring the image to the image-holding member for the purpose of improving the repeating usability of the photosensitive member, developing the transferred image and transferring the toner image to a recording material. This process is disclosed, for example in Japanese Patent Publication Nos. 7115/1957, 8204/1957 and 1559/1968.
(2) Image-holding member used in the electrophotographic process which comprises forming an electrostatic image on an electrophotographic photosensitive member in a screen form having a large number of fine openings by the predetermined electrophotographic process, applying corona charging treatment to the image-holding member through the electrostatic image to modulate the ion flow from the corona so that the electrostatic image is formed on the above image-holding member, developing such image with a toner, and transferring the toner image to a recording material thereby forming the final image. This process is disclosed, for example in Japanese Patent Publication Nos. 30320/1970 and 5063/1973, and Japanese Patent Laid Open No. 341/1976 as the electrophotographic process in which an electrostatic image corresponding to that formed on the photosensitive member is formed on the image-holding member.
(3) Image-holding member employed in the electrophotographic process which comprises forming a toner image on an electrophotographic photosensitive member, transferring the toner image to the image-holding member without directly transferring it to a recording material, and transferring the toner image from the image-holding member to a recording material followed by fixation. This process is effective, particularly for forming a color image and copying at a high speed. Most of the recording materials are usually flexible, such as for example paper and film. As a result, in the case of transferring cyan, magenta and yellow images directly onto such a recording material, it is difficult to register exactly the positions of the images. On the contrary, if the cyan, magenta and yellow images are transferred onto the image-holding member which can be formed from a hardly deformable material with the positions of the images registered, and if the transferred images are further transferred onto the recording material, a color image in which the positions of the images are more exactly registered can be obtained on the recording member. In addition, it is also effective for high speed copying that a toner image is transferred to a recording material through the image-holding member.
(4) Image-holding member employed in the electrophotographic process which comprises applying electric signal to the multi-stylus electrode to form an electrostatic image corresponding to the electric signal on the image-holding member and developing the image. The image-holding members (1)-(4) do not require a photoconductive layer.
As mentioned above, not only the electrophotographic photosensitive member, but also various members having an insulating property at the surface are employed as the image-holding member on which an electrostatic image or toner image is formed.
The image-holding member requires electric characteristics according to the nature of the electrophotographic process to be applied, and also durability is an important property of the image-holding member. The durability is required in case of repeatedly using the image-holding member. Generally, there are two factors which lower the durability of the image-holding member. One is toner remaining on the member and the other is deterioration in the electric characteristics of the member due to the corona charging.
A toner image formed on an image-holding member is transferred to a recording material such as paper and the like and then fixed to obtain a final image. Usually, the surface of the image-holding member is reused many times. At this time, a new toner image is repeatedly formed on the surface of the image-holding member each time the process for forming the toner image is repeated. Therefore, it is necessary to remove perfectly the toner remaining on the surface of the image-holding member and to clean such surface when the process cycle for the image formation is completed; that is, after the toner image is transferred. As the method of removing the remaining toner, there may be mentioned the method of wiping and scraping the toner off the surface of the image-holding member by a cleaning blade, the method of wiping off the toner by a web-like material rubbing the surface of the member, the method of wiping off the toner by a fur brush and the like, and other methods. However, when the toner remaining on the surface of the image-holding member is removed by those methods, the removing and cleaning efficiency of the methods is lowered as the frequency of repeatedly using the image-holding member is increased, and as a result, even if the surface of the image-holding member is cleaned by the methods, a portion of the toner eventually remains on the surface. The cause of that phenomenon is not yet made clear, but it is considered that since the above mentioned cleaning methods are based on the mechanical dynamic contact between the surface of the image-holding member and the cleaning means, the toner remaining on the surface of the member at the time of cleaning the surface agglomerates or fuses so that such toner adheres firmly to the surface.
If the toner remains on the surfaces of the image-holding member, a ghost image or stripe appears on the formed toner image, or the surface of the image-holding member is damaged so that such member becomes unusable.
Further, when corona discharging is repeated as the charging treatment for forming an electrostatic image on the image-holding member, the electric characteristics in the surface of the member are deteriorated due to the corona ion. This phenomenon is caused by the fact that ionized oxygen, nitrogen, carbonic acid gas, water, ammonia and the like are generated by the energy at the time when the corona ion collides directly with the surface of the image-holding member or by the corona discharging, and they adhere to the surface of the member so that the molecule of the material constituting the surface is broken or oxidized and the surface of the member is deteriorated, or the above mentioned ionized substance adsorbs moisture. As a result, the surface electric resistance of the image-holding member is lowered, and therefore such member cannot retain the electrostatic charges so that the member cannot be used as the desired image-holding member.
For the purpose of reusing the image-holding member to which the remaining toner adheres or whose electric characteristic is deteriorated, it is necessary to recover the initial surface state of the member by abrading the surface to expose the new surface.
In the conventional method for abrading the surface, it is effected in such a manner that a powdered abrasive is directly imparted to the surface, or abrasive is supplied to the surface by dispersing the abrasive in the toner or impregnating the web with the abrasive.
However, in the conventional method, drawbacks are pointed out. For example, the abrasive remains on the surface of the image-holding member. Further, when the abrasive is incorporated into the toner, the image quality of the toner image is deteriorated. Moreover, the abrasive is scattered in the electrophotographic apparatus contaminating the parts of such apparatus. In addition, it is very difficult to supply a abrasive in the constant amount to the surface of the image-holding member.